PURPOSE: To improve mutual availability by considering a calorific value and cooling capacity by permitting a personal processor module to read cooling capacity information from a docking station and to oscillate an operation frequency corresponding to the calorific value.

CONSTITUTION: ROM 75 storing information showing the cooling capacity of the docking station(DS) 2 is provided in DS 2. Plural oscillation circuits 70 and 71 and a selection circuit 72 selecting the operation frequency of CPU 12 are provided in the personal processor module(PPM) 1. When a system is started, information is read from ROM 75 and the cooling capacity of DS 2 is recognized. Then, the operation frequency of CPU 12, which becomes the calorific value that the operation of PPM 1 can guarantee, is decided in accordance with cooling capacity. The oscillators 70 and 71 corresponding to the frequency is selected by a selection circuit 75. Althrough PPM 1 cannot be used at its maximum capacity, it can be used by DS 2 with various cooling capacity, and mutual availabity can be improved.